Choosing the Best Bearing Tube Material for Your Needs

Bearing tubes are now very common steel tubes, often used in the automotive and robotic arm fields, but do you really know how to choose the right material to match your bearing tubes?

• For achieving the longest rolling contact fatigue life under clean lubrication conditions, 100Cr6 / AISI 52100, a standard bearing steel, can be considered. This is an extremely clean, integrally hardened carbon-chromium steel that conforms to ISO 683-17 standards.
• If you require higher toughness and resistance to impact damage to cope with misalignment/impact or refitting, you might consider surface hardening processes (carburizing/carbonitriding/induction hardening) instead of letting 52100 steel perform all the work.
• For bearing tubes that operate in corrosive environments such as water and salt spray for extended periods, it is recommended to use stainless steel bearing steel with an added coating. "Standard" bearing steel is not stainless steel because its chromium content is too low; typically, 3% to 12% chromium is needed to form a protective passivation film, achieving the performance of stainless steel.

How do top bearing manufacturers source bearing tubes?

The main factors that affect the procurement of bearing tubes are generally as follows:

• ASTM A295 specifies the requirements for high-carbon anti-friction bearing steels used in bearing manufacturing, including requirements for chemical composition consistency, grain size, decarburization/surface defect limits, and (if required) annealing microstructure control.
• ISO 683-17 covers the products and heat treatment conditions for ball and roller bearing steels.

Should I choose 100Cr6/52100, or a case-hardening steel?

How to select bearing tubes with the longest service life that will not crack, break, or fracture under interference fit or impact loads?

Choose based on your dominant failure mode:

1.Pick 100Cr6 / 52100 (through-hardening) when:

• Loads are high but well-distributed (good geometry)

• Lubrication is stable and relatively clean

• You need proven, widely available bearing performance

100Cr6 is the standard for ultra-precision bearing steel and is linked to the ISO 683-17 standard.

2.Pick a surface-hardening concept (carburized / carbonitrided / induction-hardened) when:

• You have shock, edge loading, misalignment, or heavy interference fits

• You want a tough core with a hard wear/fatigue-resistant surface

Surface hardening processes can create a hardness gradient (hard surface, relatively hard core), which is generally more effective in reducing structural fatigue than "higher overall hardness".

What to put in your bearing tube purchase spec?

• Steel family + target heat-treatment route (through harden vs carburize/carbonitride/induction)

• Delivery condition for machining (often spheroidize-annealed for bearing steels; specify as needed per your process)

• Mechanical property targets after heat treatment (hardness, case depth if applicable)

How clean does my bearing tube steel need to be?

For rolling contact fatigue, the cleanliness of the steel is not just an empty phrase, but one of the most important factors determining its service life.

The classic subsurface fatigue mechanism: cracks may initiate at non-metallic inclusions (unavoidable impurities during steelmaking). For more demanding applications, "high-quality" steel with lower inclusion content may be required.So how should we decide?

• Clean oil, full-film lubrication, high duty cycle: prioritize premium cleanliness (and verify it)
• Contaminated environments or thin-film lubrication: cleanliness still matters, but also prioritize surface strengthening (e.g., carbonitriding) and contamination control

What to require on the quality side?

• Inclusion rating method/limit (agree a measurable standard with your supplier)

• NDT for tubes (UT/eddy current), surface quality limits, and decarburization limits where relevant
  ASTM A295 highlights the importance of controlling decarburization and surface imperfections for bearing-quality steel product

Do I need stainless bearing tube, or can I protect standard bearing steel?

We have listed three solutions for you.

Option A — Standard bearing steel + protection (often best value)

• Use 100Cr6/52100-type base steel

• Add coatings, controlled lubrication, seals, or surface treatments

• Works well when corrosion exposure is occasional or manageable

Option B — Stainless bearing steel (when corrosion is constant or high-risk)

Ordinary bearing steel is not stainless steel because its chromium content is too low; the corrosion resistance of stainless steel comes from its higher chromium content, which forms a stable passivation oxide layer.

• Washdown, salt fog, marine exposure

• Condensation you cannot prevent

• “No-rust tolerated” product requirements

Option C — Elevated temperature / dimensional stability

If the problem lies in temperature (rather than corrosion), then the focus should be on the heat treatment stability grade and the steel/heat treatment product portfolio suitable for that temperature process, emphasizing matching solutions to temperature and stability requirements.

We've compiled a table to summarize this for you.

If you share your bearing tube drawing + duty cycle (load/speed/lube/temp/corrosion), Torich Group can recommend the best-fit material route (100Cr6/52100 vs surface-hardening vs stainless), and help you lock a purchase specification that suppliers can actually inspect and certify—so you get consistent machining, heat treatment response, and bearing life.

If you have any further questions, please contact us.